Fork position locking device



March 27, 1962 F. c. scHUsTER FORK POSITION LOCKING DEVICE Filed Sept.4, 1959 3,0Z733 Patented Mar. 27, 1962 nice 3,027,033 FGRK POSITIONLOCKING DEVICE Frank Q. Schuster, Chicago, lil., assignor toAllis-Chalmers Manufacturing Company, Milwaukee, Wis.

Filed Sept. 4, 1959, Ser. No. 838,238 2 Claims. (Cl. 214-731) Thisinvention relates to means for releasably locking the forks of anindustrial lift truck relative to the carriage whereby the lateralposition of the forks relative to the truck axis may be varied asdesired.

Various devices have been used heretofor for positioning the forks onthe carriage of a lift truck. It has been found, however, that thesepreviously known fork position devices have been deiicient in onerespect or another. For instance some are relatively expensive tomanufacture and others have not performed well in service. It isdesirable in providing a fork position locking means that the devicelend itself to being manufactured without expensive tooling, be low incost, and be suflicently sturdy of construction to stand up well in use.It is desirable that a fork positioning lock device be readilyreleasable so as to permit the operator of the fork truck to shift theforks manually and without resort to use of tools.

It is an object of this invention to provide an improved locking devicefor positioning a fork of an industrial truck in one of a variety ofpositions laterally of the trucks axis.

Another object of this invention is to provide an improved forkpositioning device which is inexpensive to manufacture.

It is a further object of this invention to provide a fork positioningdevice wherein a locking pin is releasably maintained in locking andretracted positions.

It is a further object of this invention to provide a locking pin for afork of an industrial truck of the character hereinbefore outlinedwherein the locking pin is prevented from accidental withdrawal from thefork.

Other objects and advantages of this invention will become apparent uponreading the following description in conjunction with the drawings inwhich:

FIG. l is a perspective view of a lift truck in which this invention isincorporated;

FIG. 2. is a front view of the fork locking device of this invention;

FIG. 3 is a section along lines III-Ill of FIG. 2 showing the forkposition locking pin in a locking position; and

FIG. 4 is a section showing the fork locking pin in a retractedposition.

Referring to FIG. l, there is shown an industrial lift truck 6 in whichthis invention is incorporated. This industrial lift truck has a pair offront driving wheels 7 and a pair of rear steerable wheels 8. Theoperator sits at the forward end of the truck in a seat 9 and steers thesteerable wheels 8 by means of a steering wheel 11. A vertical mast 12is mounted at the front end of the truck and carriage 16 is raised andlowered on the mast by chains 13 which are reeved over pulleys mountedon the piston of a lift ram 14. The carriage 16 has an upper forksupport 17 and a lower fork support 18 extending transversely across thefront of the truck. A pair of forks 19 are hooked over the upper forksupport 17 and are each held in position by a fork position lockingdevice 21 extending into one of a series of notches 22 formed in theupper edge of the fork support 17.

Referring to FIGS. 2, 3 and 4, fork 19 has a hook portion 23 welded tothe upper end of the main body of the fork. The hook portion 23 extendsrearwardly and downwardly to hook over an upper guide rail 24 of theupper fork support 17 in which the notches 22 are formed. The

hook portion has a horizontal surface 26 which is in sliding engagementwith a horizontal surface 27 on the fork support behindV the guide rail24. Cooperating bevel surfaces 28 and 29 on the guide rail 24 and hookportion 23', respectively, guide the fork in its lateral movement.

The fork position locking device 21 will now be described. A Verticalhole 31 is drilled in hook portion 23 so as to align with the notches 22formed in the upper fork support. A horizontal hole 32 is drilled tointersect hole 31 and extends beyond a suicient distance to form acavity 35 for receiving a coil spring 33 and detent in the form of aball 34. A pin 36 is installed in the hole 31. The pin 36 is manuallymovable by a pull ring 37 which is split to present end portions 3Swhich extend into a horizontally drilled hole 39 in the upper end of pin36. This pull ring 37 is removable by springing it outward so that theends 3S are spaced from one another a distance greater than the diameterof the upper end of the pin.

The pin 36 has a pair of recessed portions 41, 42 formed in axiallyspaced relation to one another. These axially spaced recessed portions41, 42 have carnniing surfaces 43, 44 which converge radially outward topresent an area 46 of increased diameter between the recessed portions41, 42. The lower portion 47 of the pin extends as shown in FIG. 3 intoone of the notches 22 thus locking the fork 19 against lateral shiftingrelative to the support 17. A camming surface 48 forms an abutment onthe pin 36 which as shown in FIG. 4 cooperates with the camming surfaceof ball 34 to prevent upward movement of the pin 36 out oi hole 31. Theball 34 will not move to the left since the force exerted by upwardpulling of the pin 36 against the ball has too small a horizontalcomponent to overcome the friction between the bail and wall of hole 31at point 49 and the thrust of spring 33. The force exerted by pin 36against ball 34 is represented diagrammatically by arrow 50 and itshorizontal component by arrow 51.

As shown in FIG. 3 the spring biased detent 34 releasably maintains thepin 36 in a fork locking position. When the fork truck operator insertshis finger in the pull ring 37 and pulls upwardly he moves the pin 36 toa retracted position as shown in FIG. 4. ln this position the springbiased detent 34 resiliently maintains the pin in place and aspreviously mentioned prevents upward withdrawal of the pin from the fork19. A washer 52 is in stalled on the pin 36 between the pull ring 37 andthe area 46 of increased diameter to prevent debris from falling intothe annular opening between hole 31 and the upper portion of the pin 36.The upper portion of the pin 36 is of smaller diameter than the bottomportion so as to minimize wedging of the pin in the hole 31.

In assembling the locking device the spring 33 and ball 34 are insertedin hole 32 and held in cavity portion 35 by a small rod or the likewhile the pin 36 is inserted from either end of the hole 31. The pin 36then locks the ball 34 in the cavity 35. lf the pin is installed fromthe bottom of hole 31 the pull ring 37 must tirst be removed. Onceinstalled the pin is removed by removing the pull ring 37 and thenpushing the pin 36 downwardly through the hole 31.

Thus it can be seen that there is provided an inexpensive fork hooklocking pin. By cross drilling to form a cavity 35 for the spring andball, a plug is eliminated that would otherwise be needed if the cavity35 were formed by drilling only from the exterior of the fork to thevertical hole 31. Also the lower recessed portion 42 cooperates with thedetent 34 to form a means for releasably holding the pin in an unlockedposition and also serves to prevent upward withdrawal of the pin 36 fromhole 31. Thus the pin 36 will not be accidentally lost or misplaced.

It should be understood that it is not intended to limit the inventionto the embodiment hereinabove described and shown and that the inventionincludes such other forms and modifications as are embraced by the scopeof the appended claims.

What is claimed is:

1. Means for locking a fork in one of a plurality of laterallyspacednotches in a lift truck carriage comprising: a vertical opening throughsaid fork, a cavity perpendicular to and communicating with saidvertical opening at one side thereof, a horizontal opening in said forkbetween the exterior of the latter and said vertical opening inalignment with said cavity, a round pin reciprocably disposed withinsaid vertical opening having a lower end registrable with any one ofsaid notches and presenting upper and lower annular recessed portions,camming surfaces in said recessed portions extending toward one anotherto a portion of relatively greater radius, and a spring biasedreciprocable detent disposed within said cavity and registrable,selectively, with said recessed portions in locking and retractedpositions respectively, of said pin, said lower recessed portion andsaid detent being so proportioned in relation to one another that saidpin is prevented by their engagement from being withdrawn up wardly fromsaid vertical opening, said detent being insertable into said cavitythrough said horizontal opening and said pin being manually movableaxially between said locking and retracted positions without rotation ofsaid 2. Means for locking a fork in one of a plurality of laterallyspaced notches in a lift truck carriage comprising: a vertical openingthrough said fork, a cavity perpendicular to and communicating with saidvertical opening at one side thereof, a round pin reciprocably disposedwithin said vertical opening having a lower end registrable with any oneof said notches and presenting upper and lower annular recessedportions, camming surfaces in said recessed portions extending towardone another to a portion of relatively greater radius, and a springbiased reciprocable detent disposed within said cavity and registrable,selectively, with said recessed portions in locking and retractedpositions, respectively, of said pin, said lower recessed portion andsaid detent being so proportioned in relation to one another that saidpin is prevented by their engagement from being withdrawn upwardly fromsaid vertical opening, said pin being manually movable axially betweensaid locking and retracted positions without rotation of said pin.

References Cited in the tile of this patent UNITED STATES PATENTS777,456 Wands Dec. 13, 1904 1,597,837 Staley Aug. 31, 1926 1,605,936Geschickter Nov. 9, 1925 1,631,370 Gillette June 7, 1927 2,847,138Backofen et al Aug. 12, 1958

